Fancy Tech: How to Get Rid of Exhaust Drone, works great!

Mike

Wish I knew about this when I had b&b bullets on my C6. Wife would plug her ears with her fingers for the week I had it. Plus rep!

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docaam

Thanks will plan the operation then

how do you measure like someone would need 28" or 30" or less?

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'10Anamoly

Speed of sound (typically 1100ft/sec, divided by the frequency at which drone occurs, divided by four because you want it to reflect at 1/4 the drone wavelength to cancel it out).

So for drone around 110hz-112hz (around my setup), you get to 2.5 to 2.4 ft, or 29-30".

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J. Dub

So fast intentions CBE drones.... I had no idea. Glad I didn't buy it last week.

theDreamer

Might want to check the Fast Intentions thread before making a conclusion. I get mine this week and should have a full review soon, then again there are already over a 100 reviews of the exhaust.

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Huan'z

with thedreamer. And take a look how many sets Tony sell out. I'm one of his customer still waiting for his cbe. And didn't hear anything like drone or whatever negative from other forum member. So let's wait from thedreamer. Hey bro keep us updated. Whenever u got yours and installed. Let me know so I can meet up with u. I want to hear from it and see how's good is it.

phelan

wow, shameless plug much?

So...to get the frequencies of your droning, you put a microphone to your exhaust and ran it through a spectrum analyzer (i.e. Audacity if you're not in a lab...haha) to get the peak frequencies? Out of curiosity, did you run any filters on the output, or was it all raw? How clean was the data?

Nothing serious, just piqued my curiosity. I like reading stuff like this.

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TeamARK

But this exhaust doesn't
ARK PERFORMANCE INC : 370z TRUE DUAL Prototype Teaser w/ dB Test.

Huan'z

We need to confirm with Tony of f.I and let's see what his advice. I believe Tony tried a Lot of things before he decided to make his cbe. So give him a shot and wait for his respond. That's just only my own idea.

docaam

Running FI exhausts for few months now, I can say the exhaust sounds awesome but what OP was referring to was not the normal drone (I can live with that) but vibration because of it. I do face that if I accelerate the car slowly(normal crusing) not pushing it hard as rpms has to go steady from 2k to 3k and its there for good 500 - 700, mine starts from 2200 and lasts till 2800.

This thread shouldn't be taken anything against FI as they are an awesome company with awesome product, its just people have their own preferences. My daughter(7yrs) hates this drone and avoid sitting in the car LOL. I went through doing a DYNAMAT sound proofing when upgrading the audio it has reduced this vibration (not talking about drone/sound/noise) but its still there and if Tony gives some input on this thread I am willing to do this DIY

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hr350z

Will this only work after the muffler? I have a single exhaust on my 350 and there really is no way of doing this after the muffler.

side note: not to go too far off topic will HFC's cause more drone?

kevin8086

[QUOTE='10Anamoly;650399]I did this on my car, first with 22" side branches and had no luck. After re-doing my math and using some Audacity frequency analysis, I figured out that they had to be 27-28" to work at the RPM I wanted. Longer pipes tune out frequencies lower in the RPM range. Shorter pipes (increasingly less effective) hit the higher rpms. I had the mechanic fix the pipes to 28" and VOILA, absolutely zero drone from 2200rpms to 2800rpms. At 2000rpms there is a slight rumble in the cabin, but no drone. Same at 3000rpms which changes into an aggressive purr.QUOTE]

i just had mine done and i dont get a drone until 3900-4500 depending on gear and load. how would i figure out how long i would need to make my T branches?

beemerkid

I just started on this today. Invidia gemini with FI resonated hfc's. Its not bad but its riiiight at 2800 to 2900 rpm...75to 80 mph, perfect cruising speed. So ive welded caps on so far. I wanted to package this so they sat above the mufflers, not adding extra weight to the middle, so the pipes arent an ideal length. One is 21and the other is 26. Maybe itll cut out more frequiencies because of the different lengths, I dont know. Im using 2.5 in. tubing, so the volume of the space created is pretty big. [IMG][/IMG]

kevin8086

i came up with 18" if the drone is at 4k rpms but if its going to 4500 should i shorten it?